CONCLUSIONS The bonded phase glass capillary column just described offers benefits to the routine analytical laboratory by reducing both GC analysis time and equipment “down-time”. Samples containing chlorinated pesticides and polychlorinated biphenyls can be chromatographed in about half the time required for the FDA recommended mixed phase packed column. The lack of measurable column bleed means longer column life and reduced detector contamination.
(2) C.J. Bossart, U S . Patent 3514925 (1970). (3) J. Jonsson, J. Eyem, and J. Sjoquist, Anal. Biochem., 51, 204 (1973). (4) M. Novotny and K. Grohmann, J. Chromatogr., 84, 167 (1973). (5) G. A. F. M. Rutten and J. A. Luyten, J. Chromafogr., 74,177 (1972). (6) L. Blomberg, J. Chromafogr., 115, 365 (1975). (7) F. M. Ernsberger in “Annual Review of Materials Science”, Vol. 2, Annual Review, Inc., Palo Alto, Calif., 1972, p 562. (8) “Pesticide Analytical Manual”, Vol. 1, 2d ed., U.S. Department of Health, Education, and Welfare, Food and Drug Administration, Washington, D.C., 1972, Table 311.5. (9) L. S.Ettre and E. W. March, J. Chromatogr., 91,5 (1974).
LITERATURE CITED
1976. This work was presented in part at the 169th National Meeting, American Chemical Society, Philadelphia, Pa., April 1975.
(1) M. Verzele, M. Verstappe, P. Sandra, E. Van Luchene, and A. Vuye, J. Chromatogr. Sci., 10,668 (1972).
RECEIVEDfor review June 10,1976.Accepted September 3,
Parallel Gas Chromatography-Mass Spectrometry and Gas Proportional Counting W. H. Braun,* E. 0. Madrid, and R. J. Karbowski Toxicology Research Laboratory, Health and Environmental Research, 1803 Building, Dow Chemical U.S.A., Midland, Mich. 48640
A common problem encountered in the identification of radioactive metabolites originating from metabolism/pharmacokinetics studies is the inability to demonstrate that the radioactivity is associated with a particular ion current observed in the mass spectrometer. Even after extensive cleanup procedures, a typical gas chromatograph-mass spectrometer (GC-MS) ion scan will generally contain several components of greatly varying intensity. Since in radiolabeled work the isotope enrichments are quite small, the radioactive component in a mixture cannot be distinguished by isotope ratios. Current practices require that fractions eluting from the GC be trapped for liquid scintillation counting to deter-
Injection Port
_1
-
-
(
mine the retention time of the radioactive peak. This paper describes a new technique to eliminate this laborious and time consuming process.
EXPERIMENTAL Equipment. The GC-MS used was a Finnigan Quadrupole Model 3000D equipped with a Model 6000 Data System. The gas proportional counter (GProC) was a Packard Model 894 modified by replacing Teflon lines with ?&j-in. stainless steel tubing and by replacing the septa supplied for the combustion tube with %-in. Swagelok fittings and graphite ferrules. The GC-MS and GProC were coupled with a stainless steel Hewlett-Packard effluent splitter as shown in Figure 1. Critical Operating Parameters. Helium carrier gas flow rates between 30 and 100cm3/min have been used without appreciable loss
I 11 I [
To GProC
I
Hippuric Acid
I
~
Note: Helium carrier gas may be added at the column exit to supplement the effluent stream
2284
ANALYTICAL CHEMISTRY, VOL. 48,
NO. 14,
~
~~
Retentl’on Time
Flgure 1. Schematic for parallel coupling of GC-MS and GProC
Figure 2. Total ion chromatogram and GProC scan of styrene (I4C) urinary metabolites
DECEMBER 1976
